This project will make several significant contributions to the social science, public health, and other research communities. Included among them will be interactive access to a Supersample of data from the 1990 U.S. Census long form file, and a concatenated version of the Integrated Public Use Microdata Series (IPUMS) files from the Minnesota Historical Census Projects, integrated with intelligent agents. The project encompasses two primary tasks: (1) to make more than fifty million microdata records in these data sets interactively accessible to researchers through the PDQ-Explore information system; and (2) to create PDQ-Expert, an expert system with intelligent agents, that will dynamically link data, documentation, reference materials, tutorials, and analytic tools, to facilitate access to meaningful information in public census and survey data. In this Phase II project, Public Data Queries, Inc., will: (1) Provide interactive access to massive census microdata files such as the PUMS, IPUMS, and the N ICHD 1990 Supersample, available documentation, and value-added enhancements; (2) Embed PDQ-Explore within an expert system designed to facilitate the meaningful use of these data and populated with substantive content encompassing data, documentation, analytic methods, and social issues to which the data are relevant; (3) Extend the PDQ-Explore graphical user interface, statistical capabilities, and infrastructure to accommodate the data and the expert system. PROPOSED COMMERCIAL APPLICATION: Distribution of census data is a marketable service. Additions to our PDQ- Explore data bank of the 1990 Supersample and the concatenated IPUMS, along with other census long form files that may become available, and the added-value of the enhanced documentation, an expert system, and linkage to statistical software will dramatically improve access to these data and the information within. The added features will certainly increase the marketability of PDQ-Explore.